When sending a mirrored read, the MirrorMaestro will iterate through a list of general hosts and a list of targeted hosts to send the mirror to. However, the lists may overlap meaning we can send the same mirrored read to a host multiple times. There is no value in sending the read multiple times so this is a waste of resources. We should remove all duplicates between these lists before sending the mirrors. 

Also, it looks like a node can send a targeted mirrored read to itself. Similarly, there is no value with this behavior so we should add a check to prevent a mirrored read being sent to the node that served the original read.